Lubricated blade cleaning of imaging photoconductive members

ABSTRACT

AN IMAGING SYSTEM EMPOLYING A REUSABLE ELECTROSTATOGRAPHIC IMAGING SURFACE CLEANING STATION COMPRISING AT LEAST ONE SELF-ADJUSTING FLEXIBLE CLEANING BLADE FOR PRESSURE CONTACT CLEANING OF THE IMAGING SURFACE AND MEANS TO SUPPLY A DRY SOLID LUBRICANT TO THE IMAGING SURFACE. THE LEADING FACE OF AT LEAST ONE CLEANING BLADE IS PREFERABLY POSITIONED TO FORM AN ACUTE ANGLE OF LESS THAN ABOUT 60* AND GREATER THAN ABOUT 20* WITH THE CONFRONTING PORTION OF THE IMAGING SURFACE R PLANE TANGENT TO THE IMAGING SURFACE AT THE LINE OF BLADE CONTACT.

Jan. 5, 1971 5 ROYKA ETAL 3,552,850

LUBRICATED BLADE CLEANING OF IMAGING PHOTOCONDUCTIVE MEMBERS Filed Feb.1, 1968 8 Sheets-Sheet 1 INVENTORS STEPHEN F. ROYKA BY ROBERT L.EMERALDATTORNEYS Jan. 5, 1971 5 F, RQYKA E'I'AL 3,552,851)

LUBRICATED BLADE CLEANING OF IMAGING PHOTOCONDUCTIVE MEMBERS Filed Feb.1, 1968 8 Sheets$heet 2 INVENTORS STEPHEN F. ROYKA ROBERT L EMERALDATTORNEYS Jan. 5, 1971 s ROYKA ET AL LUBRICATED BLADE CLEANING OFIMAGING PHOTOCONDUCTIVE MEMBERS Filed Feb. 1; 1968 8 Sheets-Sheet f5INVENTORS STEPHEN F. ROYKA BY ROBERT L. EMERALD ATTORNEYS Jan. 5, 1971 5ROYKA ETAL 3,552,85Q

LUBRICATED BLADE CLEANING OF IMAGING PHOTOCONDUCTIVE MEMBERS Filed Feb.1, 1968 8 Sheets-Sheet 4 STEPHEN F. ROYKA ROBERT L. EMERALD FIG. 7

INVENTORS Jan. 5, 1971 RQYKA ETAL 3552,8519

LUBRICATED BLADE CLEANING OF IMAGING PHOTOCONDUCTIVE MEMBERS 8Sheets-Sheet 5 Filed Feb. 1 1968 INVENTORS STEPHEN F. ROYKA ROBERT L.EMERALD ATTORNEYS Jan. 5, 1971 s F. ROYKA ETAL 3,552,850

LUBRICATED BLADE CLEANING OF IMAGING PHOTOCONDUCTIVE MEMBERS Filed Feb.1, 1968 8 Sheets-Sheet 6 INVENTORS STEPHEN F. ROYKA ROBERT L. EMERALD BYmm W NTfOF/VEYS Jan. 5, 1971 5 RQYKA ETAL 3,552,850

LUBRICATED BLADE CLEANING OF IMAGING PHOTOCONDU-C'ITYVE MEMBERS FiledFeb. 1, 1968 8 Sheets-Sheet M556- I 35 N 388 INVENTORS STEPHEN F ROYKABY ROBERT L. EMERALD ATTORNEYS Jan, 5, 1971 Y 5 RQYKA ETAL LUBRICATEDBLADE CLEANING OF IMAGING PHOTOCONDUCTIVE MEMBERS Filed Feb. 1, 1968 8Sheets-Sheet F,

INVENTORS STEPHEN F. ROYKA BY ROBERT L. EMERLD United States Patent3,552,850 LUBRICATED BLADE CLEANING 0F IMAGING PHOTOCONDUCTIVE MEMBERSStephen F. Royka, Fairport, and Robert L. Emerald, Rochester, N.Y.,assignors to Xerox Corporation, Rochester, N.Y., a corporation of NewYork Filed Feb. 1, 1968, Ser. No. 702,306 Int. Cl. G03g 13/08, 15/00 US.Cl. 355-15 21 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THEINVENTION This invention relates to imaging systems, and moreparticularly, to an improved cleaning device.

The formation and development of images on the surface of photoconductormaterials by electrosttic means is well known. The basic xerographicprocess, as taught by C. F. Carlson in US. Pat. 2,297,691, involvesplacing a uniform electrostatic charge on a photoconductive insulatinglayer, exposing the layer to a light-and-shadow image to dissipate thecharge on the areas of the layer exposed to the light and developing theresulting latent electrostatic image by depositing on the image afinelydivided electroscopic material referred to in the art as toner.The toner will normally be attracted to those areas of the layer whichretain a charge, thereby forming a toner image corresponding to thelatent electrostatic image. This powder image may then be transferred toa support surface such as paper. The transferred image may subsequentlybe permanently afiixed to a support surface as by heat. Instead oflatent image formation by uniformly charging the photoconductive layerand then exposing the layer to a light-and-shadow image, one may formthe latent image by directly charging the layer in image configuration.The powder image may be fixed to the photoconductive layer ifelimination of the powder image transfer step is desired. Other suitablefixing means such as solvent or overcoating treatment may be substitutedfor the foregoing heat fixing steps.

Several methods are known for applying the electroscopic particles tothe latent electrostatic image to be developed. One development method,as disclosed by E. N. Wise in U.S. Pat. 2,618,552, is known as cascadedevelopment. In this method, a developer material comprising relativelylarge carrier particles having fine toner particles electrostaticallycoated thereon is conveyed and rolled or cascaded across theelectrostatic image-bearing surface. The composition of the carrierparticles is so chosen as to triboelectrically charge the tonerparticles to the desired polarity. As the mixture cascades or rollsacross the image-bearing surface, the toner particles areelectrostatically deposited and secured to the charged portion of thelatent image and are not deposited on the uncharged or backgroundportions of the image. Most of the toner particles accidentallydeposited in the background areas are removed by the rolling carrier,due apparently, to the greater electrostatic attraction between thetoner and the carrier than between the toner and the dischargedbackground. The carrier and excess toner are then recycled. Thistechnique is extremely good for the development of line copy images.

Another method of developing electrostatic images is the imagnetic brushprocess as disclosed, for example, in US. Pat. 2,874,063. In thismethod, a developer material containing toner and magnetic carrierparticles is carried by a magnet. The magnetic field of the magnetcauses alignment of the magnetic carriers into a brush-likeconfiguration. This magnetic brush is engaged with the electrostaticimage-bearing surface and the toner particles are drawn from the brushto the latent image by electrostatic attraction.

Still another technique for developing electrostatic latent images isthe power cloud process disclosed by C. F. Carlson in US. Pat.2,221,776. In this method, a developer material comprising electricallycharged toner particles in a gaseous fluid is passed adjacent thesurface bearing the latent electrostatic image. The toner particles aredrawn by electrostatic attraction from the gas to the latent image. Thisprocess is particularly useful in continuous tone development.

Any other development method such as touchdown development as disclosedby R. W. Gundlach in US. Pat. 3,166,432 may be used were suitable.

In automatic xerographic equipment, it is conventional to employ axerographic plate in the form of a cylindrical drum Which iscontinuously rotated through a cycle of sequential operations includingcharging, exposing, developing, transfer and cleaning. The plate isusually charged with corona or positive polarity by means of a coronagenerating device of the type disclosed by L. E. Walkup in US. Pat.2,777,957 which is connected to a suitable source of high potential. Informing a powder image on the electrostatic latent image during thedevelopment step, the powder image is electrostatically transferred to asupport surface by means of a corona generating device such as thecorona device mentioned above. In automatic equipment employing arotating drum, a support surface to which a powder image is to betransferred is moved through the equipment at the same rate as theperiphery of the drum and contacts the drum at the transfer positioninterposed between the drum surface and the corona generating device.Transfer is effected by the corona generating device which imparts anelectrostatic charge to attract the powder image from the drum to thesupport surface. The polarity of charge required to effect imagetransfer is dependent upon the visual form of the original copy relativeto the reproduction and the electroscopic characteristics of thedeveloping materiel employed to effect development. For example, where apositive reproduction is to be made on the positive original, it isconventional to employ a positive polarity corona to effect transfer ofa negatively charged toner image to its support surface. When a positivereproduction from a negative image is desired, it is conventional toemploy a positively charged developing material which is repelled by thecharged areas on the plate to the discharged areas thereon to form apositive image which may be transferred by negative polarity corona. Ineither case, a residual powder image usually remains on the plate aftertransfer. Before the plate may be reused for a subsequent cycle, it isnecessary that the residul image be removed to prevent ghost images fromforming on subsequent copies. In the positive-to-positive reproductionprocess described above, the residual developer powder is tightlyretained on the plate surface by a phenomenon that is not fullyunderstood but believed to be caused by an electrical charge thatprevents complete transfer of the powder to the support surface,particularly in the image area. Discharge is substantially neutralizedby means of a corona generating device prior to the contact of theresidual powder image with a cleaning device. The neutralization of thecharge enhances the cleaning efficiency of the cleaning device.

The residual toner image is removed by electrostatographic cleaningdevices such as a brush type cleaning apparatus or web type cleaningapparatus. The typical brush cleaning apparatus is disclosed by L. E.Walkup et al. in US. Pat. 2,832,977. The brush-type cleaning meansusually comprises one or more rotating brushes which brush residualpowder from the plate into a stream of air which is exhausted through afiltering system. A typical web cleaning device is disclosed by W. P.Graft", Jr. et al. in US. Pat. 3,186,838. As disclosed by Graff, Jr. etal., removal of the residual powder on the plate is effected by passinga web of fibrous material over the plate surface.

While ordinarily capable of satisfactory cleaning electrostatographicplate surfaces, conventional electrostatographic plate cleaning devicessuffer serious deficiencies in certain areas. Most of the known cleaningdevices are complex and occupy a great deal of space in theelectrostatographic copier or duplicator. Because of the spacerequirements of the cleaning system, compact machines operating at highspeeds must be equipped with miniature high temperature fusers, thuspresenting a heat dissipation problem and also presenting a fire hazard.Further, an additional power source or a complex mechanical linkage anddrive system is required to operate the cleaning devices of the priorart. The cleaning devices employed in current commercial xerographicmachines permanently remove residual toner particles from the developersystem. Since toner material is an expensive consumable, permanentremoval of the residual toner particles from the developer system duringthe cleaning step is undesirable because it adds to the cost of machineoperation. Both the web-type and the brush cleaner systems normally donot return residual toner particles to the reusable developer mass afterthe cleaning operation. Since the web cleaner rapidly becomes loadedwith toner particles during the cleaning process, it must frequently bereplaced. Further, the web type cleaner is difficult to align with thesurface of the electrostatographic plate and uneven contact between theweb and the plate as well as uneven take-up of the web on a take-up rollis often encountered even with complex alignment apparatus. Thebrush-type cleaner must also be frequently replaced due to wear andaccumulation of toner particles on the individual brush fibers. Inaddition, an elaborate and noisy vacuum and filtering system isnecessary to collect the residual toner particles removed from theelectrostatographic plate by the brush. The large amount of tonerparticles thrown into the air by the rapidly rotating brush cleaneroften drift from the brush cleaning housing and form unwanted depositson critical machine parts. Pressure contact between cleaning webs andimaging surfaces must be kept to a minimum to prevent rapid destructionof the imaging surface. Friction resulting from high web pressures areoccasionally sufficient to cause the drum drive motor to fail due tooverheating. Thus, there is a continuing need for a better system forcleaning reusable electrostatographic surfaces.

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto provide an electrostatographic imaging system which utilizes acleaning means which overcomes the above-noted deficiencies.

It is another object of this invention to provide an improved reusableelectrostatographic plate cleaning system occupying reduced space.

It is a further object of this invention to provide an improved reusableelectrostatographic cleaning system adapted to reduce toner consumptionin automatic electrostatographic imaging machines.

It is also an object of this invention to provide a plate cleaningsystem which does not require extensive align ment or adjustment.

It is still another object of this invention to provide a more durablelonger lasting reusable electrostatographic plate cleaning system.

It is another object of this invention to provide a reusableelectrostatographic plate cleaning system which does not require a powersource.

It is a further object of this invention to provide a simple inexpensivereusable electrostatographic plate cleaning system.

It is a still further object of this invention to provide a reusableelectrostatographic plate cleaning system which is more efiicient thanknown electrostatographic plate cleaning systems.

The above objects and others are accomplished, generally speaking, byproviding an imaging system employing an improved reusableelectrostatographic imaging surface cleaning system comprising at leastone self-adjusting flexible cleaning blade in pressure contact with theimaging surface. The leading edge or face of at least one cleaning bladepreferably should be positioned to form an acute angle of less thanabout and greater than about 20 with the confronting portion of thesurface or plane tangent to the reusable imaging surface at the line ofblade contact. Thus, the residual toner particles are preferably removedby a scraping rather than a chiseling action of the cleaning blade. Asused herein, the expression leading face of the cleaning blade isintended to include that edge or face toward which the adjacent reusableelectrostatographic imaging surface has relative movement. The reusableelectrostatographic plate cleaning system of this invention includesmeans to supply a dry solid lubricant to the surface of theelectrophotographic plate. Preferably, the cleaning system of thisinvention is adapted to rapidly and continuously or intermittentlyreturn the removed residual toner material to the developer sump forreuse without undue alteration of the toner concentration in therecycled developer.

The cleaning system of this invention is particularly effective indevelopment systems employing two-component type developing materials.In carrying out the developing method of the present invention, anysuitable conventional two-component type developing material comprisingcarrier and toner particles may be used. Representative patents in whichthese developer compositions are disclosed include US. Pat. 2,618,551 toWalkup, US. Pat. 2,618,552 to Wise, US. Pat. 2,633,415 to Walkup andWise, US. Pat. 2,659,670 to Copley, US. Pat. 2,788,288 to Rheinfrank andJones and US. Reissue Pat. 25,136 to Carlson. Generally, the toners havean average particle diameter between about 1 and about 30 microns, andthe relatively larger carrier beads have an average particle diameterfrom about 50 to about 1,000 microns in diameter. Typical tonerconcentrations include a range from about 0.5 to about 10 percent byweight based on the total weight of the two-component developercomposition.

Any suitable dry solid lubricant may be employed in the system of thisinvention. The dry solid lubricant may be supplied to the interfacebetween the cleaning blade and the imaging surface by varioustechniques. For example, the dry solid lubricant may be in the form of apowder which is intimately mixed with the toner and supplied to thesurface of the imaging surface during development of the latentelectrostatic image. Alternatively, the dry solid lubricant may bedispersed throughout the photoconductive layer or suspended in aphotoconductor overcoating. As the surface of the overcoating or treatedphotoconductor gradually wears away, additional dry lubricant which wasoriginally distributed through the photoconductive or overcoating layeris exposed and made available at the interface of the cleaning blade andimaging surface. In another alternative embodiment, the dry solidlubricant may be sprinkled or smeared on the imaging surface at anypoint during the imaging cycle prior to the cleaning station. Forexample, a suitable dispenser such as a plurality of dispensersdescribed in US. Pat. 3,013,703 may be positioned over a xerographicdrum between the exposure and development stations and adapted tocontinuously or intermittently sprinkle dry solid lubricant particles onthe imaging surface. Any suitable dry solid lubricant may be employed.Hydrophobic dry solid lubricants are preferred. Further, when thelubricant may ultimately transfer to the receiving sheet, the lubricantis preferably selected from the group of materials having a (olor whichmatches the color of the receiving sheet, e.g., white lubricantparticles would be employed with white receiving sheets. Obviously,contrasting colors may be employed for novel effects if desired. Typicaldry solid hydrophobic lubricants include metal salts of fatty acids suchas zinc stearate, barium stearate, lead stearate, iron stearate, nickelstearate, cobalt stearate, copper stearate, strontium stearate, calciumstearate, cadmium stearate, magnesium stearate, zinc oleate, manganeseoleate, iron oleate, cobalt oleate, copper oleate, lead oleate,magnesium oleate, zinc palmitate, cobalt palmitate, copper palmitate,magnesium palmitate, aluminum palmitate, calcium palmitate, leadcaprylate, lead caproate, zinc linoleate, cobalt linoleate, calciumlinoleate, zinc ricolinoleate and cadmium ricolinoleate; higheraliphatic acids such as stearic acid and palmitic acid; and colloidalpyrogenic silica particles such as Cab-O-Sil available from the CabotCorporation and mixtures thereof.

Any suitable reusable electrostatographic imaging surface may beemployed in the system of this invention. Well known electrostatographicimaging surfaces include photoconductive materials such as vitreousselenium, organic or inorganic photoconductors embedded in anonphotoconductive matrix, organic or inorganic photoconductors embeddedin a photoconductive matrix and the like. Representative patents inwhich photoconductive materials are disclosed include US. Pat. 2,803,542to Ullrich, US. Pat. 2,970,906 to Bixby, US. Pat. 3,121,006 toMiddleton, US. Pat. 3,121,007 to Middleton and US. Pat. 3,151,982 toCorrsin. Generally, photoconductive materials are supported byconductive substrates. Typical conductive substrates include brass,aluminum, gold, platinum, steel, glass coated with conductive oxides,metallized non-conductive substrates, laminated sheets of metal andplastic and the like. The conductive substrate may be in the form of aflat plate, cylinder, flexible sheet or other suitable configuration.Preferably, the photoconductive surface comprises vitreous selenium,selenium alloys or mixtures of selenium and other inorganic materialsbecause superior copy quality is maintained for a greater number ofcopying or duplicating cycles.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages of the improvedreusable electrostatographic plate cleaning system of this inventionwill become even further apparent upon consideration of the followingdisclosure of the invention, particularly when taken in conjunction withthe accompanying drawings wherein:

FIG. 1 is a schematic sectional view of a xerographic reproducingapparatus employing a preferred embodiment of the cleaning bladeapparatus of the invention.

FIG. 2 is a schematic sectional view of an alternative form of theapparatus shown in FIG. 1.

FIG. 3 is a schematic sectional view of another alternative form of theapparatus shown in FIG. 1.

FIG. 4 is a schematic sectional view of still another alternative formof the apparatus shown in FIG. '1.

FIG. 5 is a schematic fragmentary sectional view of one type of cleaningblade and photoreceptor configuration according to this invention.

FIG. 6 is a schematic sectional view of an alternative form of the bladeand photoreceptor configuration shown in FIG. 5.

FIG. 7 is a schematic sectional view of another alternative form of theblade and photoreceptor configuration shown in FIG. 5.

FIG. 8 is an enlarged fragmentary sectional view of the cleaning bladeassembly shown in FIG. 1.

FIG. 9 is a schematic elevation of an alternative form of the cleaningblade assembly of this invention.

FIG. 10 is an end elevation taken on line 10-10 of FIG. 9.

FIG. 11 is a plan view of only the cleaning blade component of thecleaning blade assembly illustrated in FIG. 9.

FIG. 12 is a view in perspective of an alternative embodiment of thecleaning blade of the present invention.

FIG. 13 is a side view in elevation of another alternative embodiment ofthe blade assembly of the present invention.

FIG. 14 is a side view in elevation of still another alternativeembodiment of the blade assembly of this invention.

FIG. 15 is a plan view of the blade assembly and at a right angle withrespect to the view of FIG. 14.

FIG. 16 is a view in perpsective of a plurality of cleaning bladeholding members and blades according to another embodiment of thisinvention.

FIG. 17 is a side view in elevation of an alternative embodiment of themultiple blade system of FIG. 16.

FIG. 18 is a view in perspective of another modified form of themultiple blade embodiment of FIG. 16.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1,reference character 10 designates a rotatable xerographic drum having anouter layer 12 of photoconductive insulating material such as vitreousselenium. The drum 10 is mounted to move in the direction indicated bythe arrow. The surface of photoconductive insulating layer 12 isuniformly charged by conventional corona charging device 14 and exposedto a pattern of activating electromagnetic radiation at 16. The latentelectrostatic image formed by the exposure means 16 is developed byrotating drum 10 by means of a conventional driving means, not shown,through a developing apparatus 18 including a developer housing 20having a lower reservoir or sump portion for accumulating toner, carrierand dry lubricant particles 22. Mounted within the developer housing 20is a driven bucket-type conveyor 24 used to carry the developer materialfrom the sump to the upper portion of the developer housing 20 fromwhere the developer material is cascaded over a hopper chute 28 onto thesurface of the photoconductive layer "12.

As the developer material cascades over the drum, toner particles in thedeveloper material adhere electrostatically to the previously formedelectrostatic latent image areas on the surface of the photoconductivelayer 12 to form a visible xerographic power image; the remainingdeveloper material falling off the peripheral surface of the drum intothe sump of the developer housing 20. Toner particles consumed duringthe developing operation to form the xerographic powder images arereplenished by a toner dispenser 19 such as the dispenser described inUS Pat 3,013,703 to Hunt. In the embodiment illustrated in FIG. 1, thedry solid hydrophobic lubricant is employed in finely-divided form andadmixed with the toner particles. Thus, the dry solid lubricantparticles are introduced into the machine simultaneously with the tonerparticles by means of dispenser 19.

The developed images emerging from the developing apparatus may betransferred at a transfer station 28 to a moving paper web 30. Thetransferred power image may be permanently fixed to the web 30 by anyconventional means such as by heat fuser 32. The surface of thephotoconductor 12 is then cleaned of residual toner particles by thecleaning apparatus 34 thus completing the entire char ing, exposing,developing, transferring and cleaning cycle.

The cleaning apparatus illustrated in FIG. 1 comprises a substantiallyrectangular cleaning blade member 36 pivotally secured to a hinged bladeholder 38 by means of a shouldered screw 40. The cleaning blade 36normally rests in pressure contact with the surface of photoconductivelayer 12 due to the combined weight of the blade itself, the bladeholder 38, and cam follower 42 which is secured to blade holder 38 bysuitable means not shown. The cam follower 42 is located to one side ofthe drum and extends sufficiently below an extension of the plane of theouter surface of photoconductive layer 12 for engagement with cam 44during rotation of drum 10. If desired, the downward pressure exerted bythe combined weight of cleaning blade 36, blade holder 38 and camfollower 42 may be supplemented by spring biasing means 46. Cam 44 issecurely attached to an end of and rotates with drum 10. As the cam 44engages cam follower 42, the cam follower rides upon and follows thecurved surface of cam 44 thereby causing blade holder 38 and blade 36 tobe lifted away form the surface of photoconductive layer 12. The raisingof the blade 36 permits the ridge of residual toner particlesaccumulated by blade 36 to be transported on the moving surface ofphotoconductive layer 12 into the developing apparatus 18 where it isremoved from the surface of photoconductive layer 12 by the cascadingdeveloper. Pivotal blade movement should be limited to avoid contactbetween the blade and the imaging surface while the blade is in theretracted position. This is accomplished in this embodiment by contactbetween the blade 36 and blade holder 38. Thus, residual toner particleswhich are normally wasted by permanent removal from the xerographicmachine by conventional cleaning apparatus is immediately reclaimed eachcycle for reuse in the embodiment illustrated in FIG. 1. A removabletrough 48 may be positioned subadjacent the nine oclock position of theouter periphery of drum 10 to collect any toner particles which maygravitate away form blade 36 along the outer surface of drum 10.

In FIG. 2, another embodiment of the invention is shown wherein theouter surface of xerographic drum 50 contains at least one groove whichextends longitudinally across the drum surface parallel to the drumaxis. The development cycle illustrated in this embodiment is similar tothe system described with reference to FIG. 1. However, instead ofintroducing the dry lubricant with the toner as shown in FIG. 1,lubricant is supplied to the surface of photoconductive insulating layer54 after the photoconductive insulating layer 54 is charged by means ofcorona charging device 56 and exposed at 58 but prior ot development inthe developing apparatus 60. The dry lubricant, in particular form, isstored in dispenser 62 and controllably released by means of gate 64.

The developed images emerging from the developing apparatus 60 may betransferred at a transfer station 66 to a moving paper web 68. Theresidual untransferred toner particles adhering to the surface ofphotoconductive insulating layer 54 may then be optionally charged bymeans of a conventional corona discharge device 70 such as the devicedescribed by L. E. Walkup in US. Pat. 2,777,957. The polarity of chargeimparted to the residual toner particles by corona charging device 70'depends upon the particular results desired. Where it is desired toeliminate the inconvenience of removing and discharging the contents ofa catch trough such as trough 48 illustrated in FIG. 1, the coronadischarge device should be capable of imparting a charge polarity whichincreases the electrostatic charge adhesion between the residual tonerparticles and the surface of photoconductive insulatign layer 54 toprevent the possibility of residual toner gravitating away from thesurface of drum 50. Elimination of the trough also permits maximumrecovery of residual toner particles for reuse in the developingapparatus. If desired, the corona discharge device 70 may be used toimpart a charge polarity which reduces the electrostatic attractionbetween the residual toner particles and the surface of photoconductiveinsulating '54. The reduced attraction reduces the wiper blade pressurerequired to remove the residual toner particles and therefore extendsthe life of the photoconductor and cleaning blade. Optionally, a lightsource, not shown, may be employed in conjunction with or substitutedfor corona discharge device 70 to reduce toner particle adhesion to thephotoconductor surface.

The cleaning apparatus illustrated in FIG. 2 comprises a substantiallyrectangular cleaning blade member 72 reinforced by a U-shaped channelmember 74 and pivotally secured to a hinged blade holder 76 by means ofa shouldered screw 78. The cleaning blade 72 is biased by means of leafspring 80 to bear yieldingly against the surface of photoconductiveinsulating layer 54. As the drum 50 rotates, the residual toner on thesurface of photoconductive insulating layer 54 is dislodged andtransported by cleaningblade 72 along the drum surface toward andfinally into grooves 52. A screw 82 mounted in a lug 84 serves to limitthe lowest position to which the cleaning blade 72 can be biased by theleaf spring 80. By properly adjusting screw 8 2, the cleaning blade 72can be p0si tioned to bear yieldingly against the surface ofphotoconductive insulating layer 54 and yet be prevented from removingaccumulated toner from the grooves 52. In addition to serving as atemporary reservoir to accumulate residual toner particles, grooves 52also are adapted to remove any residual toner particles adhering to theleading face of cleaning blade 72. Removal of the residual tonerparticles from the leading face of cleaning blade 72 is effected by aWiping action between the leading face of the cleaning blade 72 andfaces 86 of grooves 52. As the drum 50- continues to rotate, theresidual toner particles collected in grooves 52 are transported intothe developing apparatus 60 where the collected toner particles areremoved by the cascading developer.

A xerographic imaging system incorporating another cleaning embodimentof this invention is illustrated in FIG. 3. In this imaging system, thecleaning apparatus is positioned in the development cycle to act onphotoconductive insulating layer 112 after charging with corona chargingdevice 114 and exposure at 116. The cleaning apparatus 110 comprises acleaning blade 117 pivotally mounted in blade holder 118 which issecurely attached to solenoid 120 by shaft 122. The solenoid 120 isactivated periodically, for example, once every cycle, to permitdisplacement of the blade holder 118 and blade 117 away from the surfaceof photoconductive insulating layer 112. The raising of blade 117permits the ridge of residual toner particles accumulated by blade 117to be transported on the moving surface of photoconductive insulatinglayer 112 into the developing apparatus 124 where it is removed from thesurface of the photoconductive layer by the cascading developer.Surprisingly good images are obtained even though a coating of residualtoner particles is carried on the surface of photoconductive insulatinglayer 112 during the charging and exposure steps. The solenoid 120 maybe energized by any suitable means. For example, in FIG. 3, cam 126 maybe driven by drum shaft 128 through a direct drive linkage to closemicro-switch 130 once every imaging cycle. Obviously, other suitableelectrically hydraulically or pneumatically activated means may besubstituted for the solenoid 120. The closing of micro-switch 130completes the illustrated circuit and permits solenoid 120 to receiveelectrical energy from a suitable source 132.

The developed images emerging from the developing apparatus 124 may betransferred at a transfer station 134 to a moving paper web 136. Thetransferred powdered image is permanently fixed to the web 136 by alarge high capacity heat fuser 138-. Since conventional bulky cleaningsystems are eliminated by the employment of the cleaning blade of thisinvention, and since the toner fusing unit is usually the principalfactor in limiting the speed of a xerographic imaging machine, theadditional space gained by employment of the cleaning blade of thisinvention permits the employment of enlarged heat fusers such as theheat fuser 138. Increased exposure time of toner images to heat energyemanating from heater elements 140 permits increased fusing speedwithout increasing the danger of fire when conventional inflammablereceiving webs such as paper web 136 are employed. The dry solidlubricant for effecting toner removal with the cleaning blade of thisinvention may be supplied to the interface between cleaning blade 117and surface of photoconductive insulating layer 112 by a component ofphotoconductive insulating layer 112 itself. For example, thephotoconductive insulating layer may be formed by co-evaporation of adry solid lubricant such as zinc stearate and selenium onto the drumsurface during manufacture. Xerographic plates containing dry solidlubricant dispersed throughout the photoconductive insulating layer areknown and described, for example, in copending application Ser. No.594,074, filed Nov. 14, 1966, by R. J. Joseph.

Referring now to FIG. 4, reference character 150 designates axerographic belt mounted to move in the direction indicated by thearrow. The surface of the xerographic belt 150 is uniformly charged byconventional corona charging device 152 and exposed to a pattern ofactivating electromagnetic radiation at full frame exposure station 154.The latent electromstatic image formed at the full frame exposurestation 154 is developed by passing xerographic belt 150 through adeveloping apparatus 156. The developed surface of xerographic belt 150is then passed through a powder cloud of dry solid lubricant in dustingchamber 158. The powder cloud of dry solid lubricant is maintained by asuitable means such as rotating brush 160 positioned within dustingchamber 158. The developed images emerging from dusting chamber 158 arethen transferred at a transfer station 162 to a moving receiving sheetor web 164. The residual untransferred toner particles adhering to thesurface of xerographic belt 150 may, if desired, then be charged bycorona discharged device 166 to neutralize the electrostatic chargeattraction between the residual toner particles and the surface ofxerographic belt 150. The charge neutralization treatment permits areduction of the wiper blade pressure required to remove the residualtoner particles. The surface of xerographic belt 150 is finally cleanedof residual toner particles by the cleaning apparatus 168 thuscompleting the entire charging, exposing, developing, lubricant treatingand cleaning cycle.

The cleaning apparatus illustrated in FIG. 4 includes a cleaning bladeassembly comprising a substantially rectangular cleaning blade member170 clamped to a pivoting head 171 by means of plate 172 and a pluralityof screws 173. Head 171 is pivotally mounted on a single shaft 174 bysuitable means not shown. Shaft 174 is in turn secured to a hinged bladeholder 176 by a press fit. The cleaning blade 170 is indirectly biasedby means of leaf spring 178 to bear yieldingly against the surface ofxerographic belt 150. As the surface of xerographic belt 150 travelspast cleaning blade member 170, the residual toner particles on thesurface of the belt are dislodged and permitted to fall into the trough180. The position of the cleaning blade 170 relative to the surface ofxerographic belt 150 may be regulated by a screw and lug assembly 182.

As discussed above, the leading edge or face of at least one cleaningblade is preferably positioned to form an acute angle of less than about90 and greater than about 20 with the surface or plane tangent to thesurface of the electrostatographic imaging layer at the line of bladecontact. The acute angle, designated by the symbol in FIG. 5, isnormally the angle between the leading edge or face 200 of cleaningblade 202 and the confronting surface 204 of a reusableelectrostatographic imaging layer 206. However, when relatively flexiblecleaning blades such as the cleaning blade 208 illustrated in FIG. 6 areemployed, the acute angle between the leading edge or face 210 andelectrostatographic imaging surface 212 of electrostatographic imaginglayer 214 should be the angle measured 0 measured as close as possibleto the line of contact between the cleaning blade and the confrontingelectrostatographic imaging surface or tangent to the imaging surface toavoid an erroneous reading such as 0 taken at a substantial distancefrom the line of blade contact. In the embodiments illustrated in FIG. 5and FIG. 6, the cleaning blades are inclined toward the ridge ofcollected toner material. It is apparent, however, that in the preferredembodiment the overall blade inclination need not be toward the ridgecollected toner particles, but may in fact be inclined away from thecollected toner particles as long as there is a leading edge or face 216even at a microscopic level to form an acute angle 0 as illustrated inFIG. 7. When the blade angle 0 exceeds about with angular knife edgedblades, uneven removal of toner particles from the surface of theimaging layer often occurs. Uneven toner removal frequently may bealleviated by increasing blade pressure. However, increased bladepressure tends to increase wear of the contacting surfaces. Theconfiguration of the cleaning blade at the point of contact need not bea sharp corner as illustrated in FIGS. 5, 6 and 7, but may be a knifeedge or even slightly rounded due to wear or as originally installed.Where a rounded or curved contacting surface of a cleaning blade surfaceis employed, the radius of curvature should preferably be lessthan about.035 inch because toner will become trapped and impacted at the shallowangle caused by the rounded edge and the drum interface. The areaenclosed by the angle increases as the radius increases. It is apparent,however, that even the blades of this invention having slightly roundedcontacting surfaces are characterized by an overall angular appearance.

It is evident from the embodiment illustrated in the drawings describedabove that the principles of the present invention include the use of atleast one self-adjusting or aligning flexible cleaning blade yieldinglybearing against a reusable electrostatographic imaging surface and ameans to directly or indirectly supply dry solid lubricant material tothe interface between the cleaning blade and the imaging surface. In theabsence of a means to provide a dry lubricant, repeated exposure of areusable electrostatographic imaging surface to the abrasive action of acleaning blade bearing yieldingly on the moving imaging surface for thelarge number of cycles required in commercial machines causes rapiddegradation of both the cleaning blade and imaging surface to the extentthat the cost of equipment replacement and degradation of imagingquality renders the system economically unfeasible lt is furtherapparent from the embodiment depicted in the drawings described above,that cleaning blades adapted to rapidly and continuously orintermittently permit the return of the removed residual toner materialto the developer sump for reuse are preferred because greater efficiencyand economy of operation are achieved. Because of the necessity foruniform and eflicient removal of residual toner particles from thesurface of reusable electrostatographic imaging surfaces in precisionhigh-speed, high-volume copying or duplicating machines, theself-adjusting feature of the cleaning blade is critical. Non-uniformand incomplete removal of residual toner particles contributes to theformation of a toner film on the imaging surface with an attendantdegradation of image quality during subsequent imaging cycles.

An enlarged fragmentary sectional view of the cleaning blade shown inFIG. 1 is illustrated in FIG. 8. In this embodiment, the flexiblerectangular cleaning blade member 36 is adhesively united to a metalplate 37 which is in turn spaced from blade holder member 38 by a washer39. Rectangular blade member 36 is pivotally secured to blade holder 38by a single shouldered screw 40 which is received by a centered threadedhole in metal plate 37. Since the diameter of the unthreaded portion 41of shouldered screw 40 is less than the diameter of the opening 43 ofblade holder 38, the flexible cleaning blade 36 is free to pivot aroundthe axis of shouldered screw 40. The ability to freely pivot around theaxis of shouldered screw 40 allows the pressure exerted by the cleaningblade 36 along the line of contact with the reusable imaging surface toequalize itself thereby uniformly removing residual toner particles fromthe imaging surface without danger of toner build up and film formation.

Another embodiment of the self-adjusting cleaning blade of thisinvention is illustrated in FIGS. 9, and 11. This cleaning blade unitincludes a flexible metal reinforcing plate 210 molded into a rubbercleaning blade 212. The metal reinforcing plate contains a plurality ofpunched out sections 214 which permit the portions of the rubbercleaning blade 212 above and below the metal reinforcing plate to adhereto each other during the cleaning blade molding operation. The flexiblemetal reinforcing plate 210 is slidably mounted in grooves 216 in thelower support arms 218. Holes 220 are located at each end of flexiblemetal reinforcing plate 210 to receive a pin 221 or a machine screw 222and a nut 226. The pin 221 or machine screw 222 and nut 226 arepositioned at the ends of flexible reinforcing plate 210 to limit thedistance of travel of flexible metal reinforcing plate 210- in grooves216 during the reusable imaging surface cleaning operation. Lowersupport arms 218 are pivotally mounted with the aid of pins 228 at theends of upper support arm 230. The upper suport arm 230 is pivotallysecured by a pin 232 to blade holder 234. Suitable means, not shown, maybe attached to the blade holder 234 to bias the cleaning blade 212toward the reusable imaging surface. The biasing pressure applied to theblade holder 234 is transmitted to the flexible metal reinforcing plate210 through upper support arm 230 and lower support arms 218. Since theflexible metal reinforcing plate 210 is flexible in a directionperpendicular to its punched surface, the biasing pressure imparted tothe flexible metal reinforcing plate 210 by lower support arms 218 issubstantially uniformly conveyed to the entire length of rubber cleaningblade 212. If desired, the number of intermediate support arms may beincreased or decreased depending upon the length of the cleaning bladeemployed. It is apparent from the foregoing discussion that the cleaningblade of this embodiment is also self-adjusting and would uniformlyremove residual toner particles from the reusable imaging surface.

FIG. 12 shows another modification of the selfdajusting cleaning bladeof this invention. In this embodiment, the flexible cleaning blade 250is sandwiched between metal plate 252 and metal plate 254. The assemblyof plates and wiper blade are secured together by a plurality of rivets256. The flexible cleaning blade 250 is divided up into a number ofindependent blade segments 258 by a plurality of slits 260. Each of theblade segments 258 may ride over any slight imperfection on the surfaceof the reusable imaging layer without adversely affecting the positionof the adjacent independent blade segments in relation to the reusableimaging surface.

Another alternative embodiment of the self-adjusting cleaning bladeassembly is illustrated in FIG. 13. A flexible cleaning blade 300 isclamped in the jaws of a blade holder 302. The jaws extend along theentire length of the cleaning blade 300 to prevent undue flexing of thecleaning blade along the direction of photoreceptor surface travel. Anadjustable plate 304 is sandwiched between the upper jaw of blade holder302 and cleaning blade 300. When highly flexible cleaning bladematerials are employed, the adjustable plate 304 should be selected fromrelatively stiff materials such as metal to provide additional supportfor the cleaning blade. Conversely, where stiff cleaning blades areemployed, the adjustable plate may comprise a soft resilient materialsuch as polyurethane sponge. The blade holder is pivotally mounted inelbow 306 which is in turn pivotally connected to a second elbow 308.The second elbow 308 is attached to a suitable support by a hingedmeans, not shown, which is similar to the hinged support illustrated inFIGS. 1, 2 and 4. Elbow 306 comprises two half shells which may besecured together by screws inserted through flanges 310, 312, and 314.As shown in the partial cut-away view of elbow 306, the split halves ofelbow 306 are either molded or machined to form a cavity in each shellwhich conforms to the configuration of the enlarged head 318 of shaft316. The cavity formed in the elbow 306 should be slightly larger thanthe enlarged portion of shaft 316 to permit the shaft 316 to freelyrotate within the cavity. The other end of the shaft 316 may be rigidlysecured by a press-fit to a T-shaped member 320 which is in turn securedby machine screws to blade holder 302. An identical arrangement isemployed to permit shaft 322 to axially rotate in elbow 306. The otherend of shaft 322 is permanently secured to elbow 308 by a press fit. Thetwo pivot points employed in the cleaning blade shown in FIG. 13 permitautomatic alignment of the cleaning blade 300 relative to the axis ofdrum 324 as well as automatic equalization of pressure along the line ofcontact between the cleaning blade 300 and the reusable surface ofelectrostatographic drum 324.

In FIGS. 14 and 15, a self-adjusting cleaning blade assembly having onepivot point instead of the two pivot points of the FIG. 13self-adjusting cleaning blade assembly is shown. A flexible cleaningblade 350 and adjustable stiffener plate 352 are clamped in the jaws ofa blade holder 354. The jaws of the blade holder 354 extend along theentire length of the cleaning blade 350 to provide suflicient supportfor the cleaning blade. The blade holder 354 is secured to a T-shapedconnecting member 356 by machine screws 358. The T-shaped member 356 ispivotally mounted on one end of a shaft 360 in a manner similar to thatillustrated in FIG. 13. The other end of shaft 360 is permanentlysecured to a hinged member 362. The hinged member 362 is biased towardthe reusable electrostatographic drum surface 364 by spring loaded pin366 which is slidably mounted in hollow sleeve 368. The pressure exertedby pin 366 may be adjusted by rotation of the threaded sleeve 368 withina threaded hole in support block 370. The hinged member 362 is hinged atpoint 372. The support block 370 and hinge half 374 are secured bysuitable means, not shown, to a support arm 376 which is mounted on ashaft 378. Shaft 378 is permanently secured to the frame of the imagingmachine by means not shown. A set screw 380 is threadably received inthe arm 376 to secure and prevent rotation of arm 376 on shaft 378. Byloosening the set screw 380, the cleaning blade assembly may be slidablyremoved from shaft 378 for repairs or adjustment of the cleaning bladeassembly or electrostatographic drum. The set screw 380 may also be usedto position the arm 367 on shaft 378 thereby permitting adjustment ofthe cleaning blade angle relative to the surface of theelectrostatographic drum. Cam 382 is securely attached to an end of androtates with drum 364. As the drum 364 rotates in the direction shown bythe arrow, carn 382 engages a roller cam follower 384 which rotates on asupporting pin 386 which is secured to the lower bifurcated portion ofarm 388 which extends downwardly from one end of hinged member 362. Asthe cam 382 engages roller cam follower 384, the roller cam followerrides upon and follows the curved surface of cam 382 thereby causing'arm388 as well as the cleaning blade 350 to be lifted away from the surfaceof the electrostatographic drum 364. The raising of the blade 350permits the ridge of residual toner particles accumulated by blade 350to be transported on the moving surface of electrostatographic drum 364into the developing apparatus, not shown, where it is removed from thesurface by the cascading developer. Since the blade holder 354 positionsthe leading face 390 of cleaning blade 350' at an angle of about 135with respect to the axis of shaft 360, the function of the two pivotpoints employed in the cleaning blade assembly of FIG. 13 isaccomplished with a single pivot point, thereby permitting automaticalignment of the cleaning blade 350 relative to the axis of drum 364 aswell as automatic equalization of pres sure between the cleaning blade350 and the reusable surface of electrostatographic drum 364 along theline of blade-drum contact. In other words, the blade 350 has twoadaptations to the imaging surface, one transversely or generallycircumferentially of the imaging surface and one axially across thewidth thereof.

If desired, a plurality of cleaning blades may be employed to clean theresidual toner particles from the surface of the reusable imagingsurface. In the embodiment depicted in FIG. 16, each of the cleaningblade assemblies 400, 402 and 404 extend across the entire axial lengthof the electrostatographic imaging drum. The blade material employed ineach of the cleaning blade assemblies need not be identical to thematerials employed in the other cleaning blades. For example, cleaningblade 406 may comprise a flexible but relatively stiff material such aspolyurethane which removes the bulk of the residual toner particles onthe surface of electrostatographic drum 408 whereas the cleaning blades410 and 412 of cleaning blade assemblies 402 and 404, respectively, maycomprise relatively soft material which removes the residual tonerparticles, if any, not removed by cleaning blade 406. Where a highlycompact multiple cleaning blade system is desired the cleaning bladeassembly shown in FIG. 17 may be substituted for the plurality ofcleaning blade assemblies of FIG. 16. The cleaning blade assemblyillustrated in FIG. 17 comprises two cleaning blades 420 and 422 clampedin the jaws of a single blade holder 424. The jaws extend along theentire length of the cleaning blades 420 and 422 to prevent undueflexing of the cleaning blade. Adjustable stiffener plates 426 and 428may be sandwiched between the upper surface of each blade and the jawsof the blade holder. As discussed above, the stiffening blades provideadditional support for the cleaning blades, particularly when highlyflexible cleaning blade materials are employed.

An alternative multiple cleaning blade system is shown in the isometricview in FIG. 18. Each of the cleaning blades 450, 452 and 454 carried bythe cleaning blade holders 456, 458 and 460, respectively, extendsacross a portion of the axial length of reusable electrostatographicdrum 462. The cleaning blades are staggered and overlapped to insurethat the entire imaging surface of the reusable electrostatographic drum462 are contacted by the blades. The reusable electrostatographic drum462 contains staggered grooves or depressions 464, 466 and 468. Thesegrooves or depressions are positioned to permit each of the cleaningblades to ride over the grooves rather than into the grooves. Forexample, cleaning blade 452 is prevented from riding down into thegrooves 464 and 468 by the undepressed surface of reusableelectrostatographic drum 462 located between grooves 464 and 468.Similarily since the groove 466 is shorter than the length of cleaningblade 452, the undepressed surface of reusable electrostatographicimaging drum 462 located at each end of groove 466 prevents the cleaningblade 452 from riding down into groove 466. The groove arrangement shownin FIG. 18 eliminates the need of a means to limit the lowest positionof cleaning blade travel since the undepressed portions of the surfaceof reusable electrostatographic drum 462 prevent the cleaning bladesfrom entering the grooves and removing accumulated toner. As theelectrostatographic drum 462 continues to rotate, the residual tonerparticles collected in the grooves 464, 466 and 468 are transported intothe developing apparatus, not shown, where the coll4 lected tonerparticles are removed by the cascading developer.

Although most of the illustrations discussed above are directed toelectrostatographic imaging systems employing a cascade developmentstation, it is apparent that other development techniques such as themagnetic brush, fiber brush, powder cloud and touchdown developmentsystems described above may be used where suitable. However, the'cascade type development system is preferred because of the rapid returnof residual toner particles to the main body of developer and uniformmixing of the main body of developer with the recovered toner for reuse.The carrier bead trapping and attendant electrostatographic imagingsurface bead scratching problems encountered. with the prior artcleaning web systems are completely obviated'by the cleaning bladesystems of the present invention. Permanent removal of residual toner byconventional web and brush cleaning systems is also eliminated byemploying the preferred cleaning system of this invention.

Any suitable non-metallic flexible cleaning blade material may beemployed in the cleaning system of this invention. Typical non-metallicflexible materials include:

polysiloxane rubber polyurethane rubber, polytetrafluoroethylene resin,polytrifluorochloroethylene resin, styrene-butadiene rubber, nitrilerubber, nitrile/silicone rubber, flexible polyurethane foam,polyethylene resin and blends, mixtures and copolymers thereof. Theblade should be sufficiently soft to minimize abrasion of reusableimaging surfaces, particularly selenium type imaging surfaces.Preferably, the blade material should have a Shorehardness of less thanabout D65. Considerable latitude in blade thickness is permissible.However the blade should be sufliciently thick to avoid collapse of theblade on the imaging surface under the blade pressure conditionsemployed. Obviously, greater latitude in flexi bility of the bladematerial is available when the stiffening members described above areemployed in the blade holder. The cleaning blade pressure upon thesurface of the reusable imaging surface can vary considerably.Generally, the minimum pressure necessary for effective removal of thetoner particles from the reusable imaging surface is preferred becauseundue Wear of the reusable imaging surface is avoided. Satisfactoryresults have been obtained when the weight of a three pound cleaningblade assembly, such as the cleaning blade assembly illustrated in FIG.1, was the only source of pressure exerted on the cleaning blade. Thecorner between the leading face of the cleaning blade and the blade endor edge must be sufficiently abrupt to perform an effective scrapingaction as opposed to a smearing action. However, satisfactory resultsare obtained when the angular imaging surface engaging edge of thecleaning blade is slightly rounded due to wear as described above. Thus,effective toner removal is maximized when the surface area of theportion of the blade in contact with the imaging surface is minimized. Asurprisingly large latitude of operating speeds is permissible with thecleaning blade of this invention. Extremely high cleaning efliciency isachieved with cleaning blade to reusable imaging surface relative speedsof up to about 5 feet per second.

The following examples further specifically define and describe theimaging system of the present invention for deveoping electrostaticlatent images with toner, transferring the resulting toner images to areceiving surface and thereafter cleaning the reusable imaging surfacewith a flexible self-adjusting cleaning blade. Parts and percentages areby weight unless otherwise indicated. These examples, other than thecontrol examples, are intended to illustrate the various preferredembodiments of the present invention.

In the following Examples I through IV, are carried out in a copyingmachine described in detail in US. Pat. 3,099,856. A standard Xerox 813cleaning web is employed in the control example and a self-aligningpolyurethane elastomer. Disogrin, cleaning blade is substituted for thecleaning web in the examples illustrating the preferred embodiments ofthis invention,

EXAMPLE I The vitreous selenium drum of a copying machine is coronacharged to a voltage of about 800 volts and exposed to alight-and-shadow image to form an electrostatic latent image. Theselenium drum is then rotated through a cascade development station. Adeveloper comprising a toner comprising a styrene-butyl methacrylatecopolymer, polyvinyl butyral, and carbon black prepared by the methoddisclosed in Example I of U.S. Pat. 3,079,- 342 and carrier beadsprepared by the process disclosed in U.S. Pat. 2,618,551 is employed inthe developer station. After the electrostatic latent images aredeveloped in the developing station, the resulting toner images aretransferred to a sheet of paper at a transfer station. The residualtoner powder remaining on the selenium drum after passage through thetransfer station is removed by a conventional Xerox 813 cleaning web ata cleaning station. A detailed description of this type of imagingsystem is set forth in U.S. Pat. 3,099,856. The drum is rotated at aconstant linear surface speed of approximate- 1y 3 inches per secondduring the imaging cycle. The imaging cycle is repeated for 10,000cycles. This test serves as a control. Microscopic examination of theselenium surface after 10,000 cycles, reveals considerable wear with alarge number of deep scratches apparently caused by carrier beadstrapped between the cleaning web and the selenium drum surface. Thequantity of toner lost with this cleaning system is found to be about 87grams.

EXAMPLE II The test described in Example I is repeated with a freshselenium drum, zinc stearate powder in the developer and a self-aligningcleaning blade assembly substituted for the cleaning web. The zincstearate is incorporated into the developer by simply tumbling about 99parts toner particles with about 1 part by weight, based on the totalweight of the toner, of powdered zinc stearate in a sealed horizontalrotating cylinder. The cleaning blade assembly employed is similar tothe cleaning blade assembly illustrated in FIG. 1 except for theelimination of spring biasing means 46. The blade material is arectangular strip of polyurethane elastomer, Disorgrin, (available fromDisorgrin Industries) having a thickness of about inch. The leading faceof the cleaning blade is positioned to form an acute angle of about 60with the confronting portion of the selenium drum surface at the line ofblade contact. Although the spring biasing means shown in FIG. 1 is notemployed, sufficient pressure is applied to the blade by the weight ofthe blade assembly to effectively remove residual toner particles fromthe drum surface. The total Weight of the blade assembly is found to beabout 3 pounds. A cam is securely attached to one end of the seleniumdrum for contact with a cam follower attached to the blade assembly.Since the cam is securely attached to the selenium drum, the cam causesthe blade to lift away from the selenium surface once every imagingcycle to permit the toner collected by the blade to be transported bythe drum surface into the developing housing where it is picked up bythe cascading developer. The modified machine is operated for 10,000cycles and the drum is then removed for examination. Microscopic studiesof the selenium surface indicate only slight wear of the surface. Nodeep scratches can be found anywhere on the selenium surface. Thequantity of toner lost with this cleaning system is found to be about3.5 grams. Thus, the toner lost in this modified machine is about 24times less than the loss in the machine described in Example I.

EXAMPLE III The procedure described in Example II is repeated with afresh drum and fresh developer. In addition, a powder dispenser ispositioned between the cleaning blade assembly and the exposure station.The dispenser is regulated to sprinkle a thin powder film of zincstearate on the selenium surface during the imaging cycle. After 10,000cycles, a microscopic examination of the imaging surface revealssubstantially the same degree of wear observed on the imaging surfacedescribed in Example II.

EXAMPLE 1v 1 The test described in Example I is repeated with a modifiedselenium drum, zinc stearate powder in the developer and a self-aligningcleaning blade assembly substituted for the cleaning web. The zincstearate is incorporated into the developer by simply tumbling about 100parts toner particles with about 1 part by weight, based on the totalweight of the toner, of zinc stearate in a sealed horizontal rotatingcylinder. The cleaning blade assembly employed is similar to thecleaning blade assembly illustrated in FIG. 2. The selenium drum ismodified to provide two adjacent and parallel depressions extendingaxially along the length of the drum. These depressions have asemi-circular cross section with a radius of curvature of about .062inch. The blade material is a rectangular strip of natural rubber havinga thickness of about inch. The leading face of the cleaning blade ispositioned to form an acute angle of about with the confronting portionof the selenium drum surface at the line of blade contact. The totalpressure exerted upon the blade in a direction parallel to the drumradius at the line of contact is about 3 pounds as determined by aspring scale. A corona discharge electrode is positioned between thetransfer station and the cleaning station to neutralize electric chargecarrier by residual toner particles. This neutralization is accomplishedby operating the corona discharge electrode at a high voltagealternating potential of about 60 cycles AC and 6,000 peak volts. Thevoltage is biased at a slightly negative current, such that the positivecurrent is about 10 microamps and the negative current is about 12microamps. A limit is provided to permit the cleaning blade to pass overthe grooves without substantial penetration, thereby preventing thecleaning blade from scooping out toner particles from the grooves. Thetoner particles collected in the grooves are picked up by the cascadingdeveloper in the developing housing. The modified drum is operated for10,000 cycles and the drum is then removed for examination. Microscopicstudies of the selenium surface indicate substantially the same degreeof wear observed on the imaging surface described in Example II. Thequantity of toner loss in this cleaning system is considerably less thanthe loss in the machine described in Example I.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, other modifications andramifications of the present invention will appear to those skilled inthe art upon a reading of the disclosure. These are intended to beincluded within the scope of this invention.

What is claimed is:

1. An electrostatographic imaging apparatus comprismg:

an annular recyclicable layer having an electrostatographic imagingsurface and -a plurality of processing stations;

means to support said recyclicable layer and to effect relative movementbetween said electrostatographic imaging surface and said stations;

a first of said stations comprising rneans for forming an electrostaticlatent image on said imaging surface;

a second of said stations comprising means for applying toner particlesto said imaging surface to develop said electrostatic latent image;

a third of said stations comprising for transferring said developedtoner image from s id imaging surface to a receiving surface;

a fourth of said stations comprising at least one cleaning bladeassembly for removing residual particles from at least a portion of saidimaging surface, said cleaning blade assembly comprising at least oneflexible cleaning blade and cleaning blade aligning means, said cleaningblade having a substantially angular imaging surface engaging edge andbeing elongated axially along the Width of said imaging layer and saidcleaning blade aligning means being adapted to permit said cleaningblade to align itself substantially parallel to said imaging surface andaxially along the width of said imaging layer when said cleaning bladeis engaged with said imaging surface;

means for periodically displacing said cleaning blade toward and awayfrom said imaging surface thereby permitting residual particlesaccumulated by said cleaning blade to be transported on said imagingsurface past said cleaning blade; and

means to supply a dry solid lubricant to said electrostatographicimaging surface.

2. An electrostatographic imaging apparatus according to claim 1 inwhich said means for supporting said cleaning blade assembly is adaptedto position the leading face of said cleaning blade at an angle betweenabout 20 and about 90 with a tangential plane to said imaging surface atthe line of cleaning blade contact when said cleaning blade is engagedwith said imaging surface.

3. An electrostatographic imaging apparatus according to claim 1 inwhich said means for periodically displacing said cleaning bladecomprising a cam secured to said means to support said annularrecyclicable layer and a cam follower secured to said cleaning bladeassembly and positioned to permit a sufiicient degree of engagement ofsaid cam following with said cam to displace said cleaning blade awayfrom said imaging surface.

4. An electrostatographic imaging apparatus comprising:

an annular recyclicable layer having an electrostatographic imagingsurface and at least one groove extending axially along said imagingsurface and a plurality of processing stations;

means to effect relativemovement between said electrostatographicimaging sun-face and said stations;

a first of said stations comprising means for forming an electrostaticlatent image on said imaging surface;

a second of said stations comprising means for applying toner particlesto said imaging surface to develop said electrostatic image;

a third of said stations comprising means for transferring saiddeveloped toner image from said imaging surface to a receiving surface;

a fourth of said stations comprising at least one cleaning bladeassembly for removing residual particles from at least a portion of saidimaging surface, said cleaning blade assembly comprising at least oneflexible cleaning blade, cleaning blade aligning means and cleaningblade limiting means, said cleaning blade having substantially angularimaging surface engaging edge and being elongated axially along thewidth of said imaging layer when said cleaning blade is engaged withsaid imaging surface and said cleaning blade limiting means beingadapted to limit penetration of said cleaning blade into said groove;and

means to supply a dry solid lubricant to said electrostatographicimaging surface.

5. An electrostatographic imaging apparatus according to claim 4 inwhich said means for supporting said cleaning blade assembly is adaptedto position the leading face of said cleaning blade at an angle betweenabout 20 and about 90 with a tangential plane to said imaging surface atthe line of cleaning blade contact when said cleaning blade is engagedwith said imaging surface.

6. An electrostatographic imaging apparatus according to claim 4 inwhich a plurality of parallel grooves extend axially along said imagingsurface.

7. An electrostatographic imaging apparatus according to claim 6 inwhich the length of each of said plurality of grooves is less than thewidth of said electrostatographic imaging surface.

8. An electrostatographic imaging apparatus according to claim 7 inwhich the plurality of said flexible cleaning blades are located at saidfourth of said stations.

9. An electrostatographic imaging apparatus according to claim 8 inwhich the length of each of said cleaning blades is less than the widthof said electrostatographic imaging surface.

10. An electrostatographic imaging apparatus according to claim 9 inwhich the length of each of said grooves is less than the length of eachof said flexible cleaning 0 blades.

11. A photoconductive imaging apparatus comprising:

a recyclicable layer having a dry photoconductive imaging-surface and aplurality of processing stations;

means to effect relative movement between said photoconductiveimaging-surface and said stations;

a first of said stations comprising means for forming an electrostaticlatent image on said photoconductive imaging-surface;

a second of said stations comprising means for applying dry tonerparticles to said photoconductive imagingsurface to develop saidelectrostatic latent image whereby a developed toner image is formed;

a third of said stations comprising means for transferring saiddeveloped toner image from said photoconductive imaging-surface to areceiving surface;

a fourth of such stations comprising a cleaning assembly for removingdry residual particles from said dry photoconductive imaging-surface,said cleaning assembly comprising a pressure applying means and at leastone flexible cleaning blade/having a substantially angularimaging-surface engaging edge aligned parallel to and in pressurecontact with said photoconductive imaging-surface, said pressureapplying means being adapted to apply suflicient pressure to saidflexible cleaning blade to remove substantially all of said residualparticles on the portion of said photoconductive imaging-surface incontact with said flexible cleaning blade; and

means to supply a dry solid lubricant to said photoconductiveimaging-surface.

12. A photoconductive imaging apparatus comprising:

an annular recyclicable layer having a dry photoconductiveimaging-surface and a plurality of processing stations;

means to effect relative movement between said photoconductiveimaging-surface and said stations;

a first of said stations comprising means for forming an electrostaticlatent image on said photoconductive imaging-surface.

a second of said stations comprising means for applying dry tonerparticles to said photoconductive imaging-surface to develop saidelectrostatic latent image whereby a developed toner image is formed;

a third of said stations comprising means for transferring saiddeveloped toner image from said photoconductive imaging-surface to areceiving surface;

a fourth of said stations comprising a cleaning assembly for removingdry residual particles from said dry photoconductive imaging surface,said cleaning assembly comprising a pressure applying means and at leastone flexible cleaning blade having a substantially angularimaging-surface engaging edge aligned parallel to and in pressurecontact with said photoconductive imaging-surface, said angularimaging-surface engaging edge being elongated axially along the width ofsaid annular recyclicable layer, said pressure applying means beingadapted to apply suflicient pressure to said cleaning blade to removesubstantially all of said residual particles on the portion of 19 a saidphotoconductive imaging-surface in contact with said fiexible cleaningblade; and

means to supply a dry solid lubricant to said photoconductiveimaging-surface.

13. A photoconductive imaging apparatus according to claim 12 in whichsaid cleaning blade assembly is adapted to position the leading face ofsaid cleaning blade at an angle between about 20 and about 90 with atangential plane to said photoconductive imaging-surface at the line ofcleaning blade contact when said cleaning blade is engaged with saidphotoconductive imaging-surface.

14. A photoconductive imaging apparatus according to claim 12 in whichsaid annular recyclicable layer is a belt.

15. A photoconductive imaging apparatus according to claim 12 in whichsaid annular recyclicable layer is a cylinder.

16. A photoconductive imaging apparatus according to claim 12 furtherincluding a corona discharge electrode positioned and disposed to applyelectrostatic charge to said photoconductive imaging-surface prior toremoval of residual particles from said photoconductive imagingsurfiaceby said cleaning blade.

17. A photoconductive imaging apparatus according to claim 12 in whichsaid fourth of said stations is positioned adjacent to the saidphotoconductive imaging-surface between said first of said stations andsaid second of said stations.

18. A photoconductive imaging apparatus according to claim 12 in whichsaid fourth of said stations is positioned adjacent to the saidphotoconductive imaging-surface between said third of said stations andsaid first of said stations.

19. A photoconductive imaging apparatus according to claim 12 in which atoner catch-tray is positioned subadjaccnt said fourth of said stationsto catch any residual particles falling away from said fourth of saidstations.

20. A photoconductive imaging apparatus according to claim 12 in whichsaid cleaning blade comprises a row of blade segments.

21. A photoconductive imaging apparatus according to claim 12 in whichsaid means for applied dry toner particles is adapted to cascade saidtoner particles and carrier particles over a portion of saidphotoconductive imaging surface.

References Cited UNITED STATES PATENTS 3,438,706 10/1966 Hiroshi Tanakaet a1, 35511 2,576,047 11/ 1951 Schaffert 15-1.5X 2,987,660 6/1961Walkup 3553 3,306,193 2/1967 Rarey 118--637 3,378,876 4/1968 Sisson15256.51 3,382,360 5/1968 Young 355--3X JOHN M. HORAN, Primary ExaminerR. P. GREINER, Assistant Examiner U.S. Cl. X.R. 151.5, 256.51

